The invention relates to a needle holder for a sewing machine, in particular an industrial sewing machine. Referring to sewing machines, the needle holder, the stitch plate, the gripper and the needle guard must be positioned precisely relative to each other, in order to ensure reliable stitching, especially when sewing occurs at a high sewing speed and with a high number of stitches. If the adjustment of the position of the gripper relative to the needle is inadequate, faulty stitching, needle and thread breakage, as well as damage to the gripper and the needle guard may occur.
Referring in particular to the thickness of sewing needles, they are selected in view of the material that is to be sewn. Accordingly, there is the necessity for the use of sewing needles having different thicknesses on one and the same sewing machine.
In the vicinity of its eye, the sewing machine needle has a furrow, into which sinks the gripper while the stitch is being produced in order to pick up a thread that has been pushed through the sewing material. Needles of different thicknesses have a furrow with different depths. The base or bottom of the furrow thus has a different position depending on the respectively different sewing needle that is used.
This is obvious from document DE 103 34 023 A1 that discloses systems for the manufacture of needles having different thicknesses. When using these sewing needles, the gripper position need not be adapted to the respectively used needle thickness. Referring to needles having a large needle diameter in the region of the furrow, the use of the teaching of DE 103 34 023 leads to a small needle cross-section, compared with the needle cross-section in the region of the needle shaft. This increases the susceptibility to breakage, in particular in the case of needles having a large needle diameter (Nm).
Referring to home sewing machines, needles have a shank with a flat area to avoid a gripper adjustment. Referring to sewing machine needles having different gauges (needles with different nominal diameters), this flat area has a respectively different size in order to ensure that a gripper adjustment is not required when needles of different thicknesses are to be used. Referring to industrial sewing machines, however, as a rule, needles having a cylindrical shank are required. Consequently, the needle holder uniformly defines the central axis of all the sewing needles.
The adjustment of a gripper to adapt it to sewing needles of different gauges, as a rule, involves a significant amount of work and, in addition, requires a skilled operator. In particular, referring to lockstitch machines having a vertically arranged gripper axis, the subsequent adjustment of the gripper and the needle guard is particularly complex, thus resulting in down times and a significant setup effort.
DE Patent 872 147 discloses a sewing machine with a needle bar that can be shifted vertically in slide bearings. At its lower end, the needle bar supports a needle holder with a clamp screw for attaching a sewing needle. The slide bearings for the shiftable support of the needle bar are provided on a guide element which can be brought into the desired spatial position by means of adjusting screws, thus allowing an adjustment of the needle. Any subsequent adjustment of the needle, however, requires skilled knowledge and access to the interior of the sewing machine housing.
Referring to DE Patent 856 828 and U.S. Pat. No. 3,713,407, each discloses a sewing machine comprising a needle bar being provided on its lower end with a pocket bore that receives the shank of a sewing needle. Transversely to the pocket bore is a threaded bore for the accommodation of a clamp screw. Thus, the position of the sewing needle relative to the needle bar is defined.
GB Patent 1050003 discloses a sewing machine comprising a needle bar supported in an adjustable guide. The connection between the needle bar and the sewing needle is achieved simply by a conventional clamp screw. The adjustment of the needle bar guide requires access to the interior of the sewing machine and skilled knowledge.
Considering this, it is the object of the invention to provide an option that allows the use of needles of different gauges on sewing machines, in particular industrial sewing machines, without requiring a subsequent adjustment of the gripper.